/*
 * Copyright 2010-2017 JetBrains s.r.o.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.jetbrains.kotlin.resolve.calls.results

import it.unimi.dsi.fastutil.Hash
import it.unimi.dsi.fastutil.objects.ObjectOpenCustomHashSet
import org.jetbrains.kotlin.builtins.KotlinBuiltIns
import org.jetbrains.kotlin.builtins.StandardNames
import org.jetbrains.kotlin.builtins.UnsignedTypes
import org.jetbrains.kotlin.descriptors.*
import org.jetbrains.kotlin.descriptors.synthetic.SyntheticMemberDescriptor
import org.jetbrains.kotlin.resolve.DescriptorEquivalenceForOverrides
import org.jetbrains.kotlin.resolve.OverridingUtil
import org.jetbrains.kotlin.resolve.calls.context.CheckArgumentTypesMode
import org.jetbrains.kotlin.resolve.descriptorUtil.isTypeRefinementEnabled
import org.jetbrains.kotlin.resolve.descriptorUtil.varargParameterPosition
import org.jetbrains.kotlin.types.KotlinType
import org.jetbrains.kotlin.types.TypeUtils
import org.jetbrains.kotlin.types.checker.KotlinTypeRefiner
import org.jetbrains.kotlin.types.model.KotlinTypeMarker
import org.jetbrains.kotlin.types.model.requireOrDescribe
import org.jetbrains.kotlin.util.CancellationChecker
import java.util.*

open class OverloadingConflictResolver<C : Any>(
    private val builtIns: KotlinBuiltIns,
    private val module: ModuleDescriptor,
    private val specificityComparator: TypeSpecificityComparator,
    private val platformOverloadsSpecificityComparator: PlatformOverloadsSpecificityComparator,
    private val cancellationChecker: CancellationChecker,
    private val getResultingDescriptor: (C) -> CallableDescriptor,
    private val createEmptyConstraintSystem: () -> SimpleConstraintSystem,
    private val createFlatSignature: (C) -> FlatSignature<C>,
    private val getVariableCandidates: (C) -> C?, // for variable WithInvoke
    private val isFromSources: (CallableDescriptor) -> Boolean,
    private val hasSAMConversion: ((C) -> Boolean)?,
    private val kotlinTypeRefiner: KotlinTypeRefiner,
) {

    private val isTypeRefinementEnabled by lazy { module.isTypeRefinementEnabled() }

    private val resolvedCallHashingStrategy = object : Hash.Strategy<C> {
        override fun equals(call1: C?, call2: C?): Boolean =
            if (call1 != null && call2 != null)
                call1.resultingDescriptor == call2.resultingDescriptor
            else
                call1 == call2

        override fun hashCode(call: C?): Int = call?.resultingDescriptor?.hashCode() ?: 0
    }

    private val C.resultingDescriptor: CallableDescriptor get() = getResultingDescriptor(this)

    // if result contains only one element -- it is maximally specific; otherwise we have ambiguity
    fun chooseMaximallySpecificCandidates(
        candidates: Collection<C>,
        checkArgumentsMode: CheckArgumentTypesMode,
        discriminateGenerics: Boolean
    ): Set<C> {
        candidates.setIfOneOrEmpty()?.let { return it }

        val fixedCandidates = if (getVariableCandidates(candidates.first()) != null) {
            findMaximallySpecificVariableAsFunctionCalls(candidates) ?: return LinkedHashSet(candidates)
        } else {
            candidates
        }

        val noEquivalentCalls = filterOutEquivalentCalls(fixedCandidates)
        val noOverrides = OverridingUtil.filterOverrides(
            noEquivalentCalls,
            isTypeRefinementEnabled,
            cancellationChecker::check
        ) { a, b ->
            val aDescriptor = a.resultingDescriptor
            val bDescriptor = b.resultingDescriptor
            // Here we'd like to handle situation when we have two synthetic descriptors as in syntheticSAMExtensions.kt

            // Without this, we'll pick all synthetic descriptors as they don't have overridden descriptors and
            // then report ambiguity, which isn't very convenient
            if (aDescriptor is SyntheticMemberDescriptor<*> && bDescriptor is SyntheticMemberDescriptor<*>) {
                val aBaseDescriptor = aDescriptor.baseDescriptorForSynthetic
                val bBaseDescriptor = bDescriptor.baseDescriptorForSynthetic
                if (aBaseDescriptor is CallableMemberDescriptor && bBaseDescriptor is CallableMemberDescriptor) {
                    return@filterOverrides Pair(aBaseDescriptor, bBaseDescriptor)
                }
            }
            Pair(aDescriptor, bDescriptor)
        }
        if (noOverrides.size == 1) {
            return noOverrides
        }

        val maximallySpecific = findMaximallySpecific(noOverrides, checkArgumentsMode, false)
        if (maximallySpecific != null) {
            return setOf(maximallySpecific)
        }

        if (discriminateGenerics) {
            val maximallySpecificGenericsDiscriminated = findMaximallySpecific(noOverrides, checkArgumentsMode, true)
            if (maximallySpecificGenericsDiscriminated != null) {
                return setOf(maximallySpecificGenericsDiscriminated)
            }
        }

        return noOverrides
    }

    // Sometimes we should compare "copies" from sources and from binary files.
    // But we cannot compare return types for such copies, because it may lead us to recursive problem (see KT-11995).
    // Because of this we compare them without return type and choose descriptor from source if we found duplicate.
    fun filterOutEquivalentCalls(candidates: Collection<C>): Set<C> {
        candidates.setIfOneOrEmpty()?.let { return it }

        val fromSourcesGoesFirst = candidates.sortedBy { if (isFromSources(it.resultingDescriptor)) 0 else 1 }

        val result = LinkedHashSet<C>()
        outerLoop@ for (meD in fromSourcesGoesFirst) {
            cancellationChecker.check()
            for (otherD in result) {
                val me = meD.resultingDescriptor.originalIfTypeRefinementEnabled
                val other = otherD.resultingDescriptor.originalIfTypeRefinementEnabled
                val ignoreReturnType = isFromSources(me) != isFromSources(other)
                if (DescriptorEquivalenceForOverrides.areCallableDescriptorsEquivalent(
                        me,
                        other,
                        allowCopiesFromTheSameDeclaration = isTypeRefinementEnabled,
                        ignoreReturnType = ignoreReturnType,
                        kotlinTypeRefiner = kotlinTypeRefiner
                    )
                ) {
                    continue@outerLoop
                }
            }
            result.add(meD)
        }

        return result
    }

    private val CallableDescriptor.originalIfTypeRefinementEnabled get() = if (isTypeRefinementEnabled) original else this

    private fun Collection<C>.setIfOneOrEmpty() = when (size) {
        0 -> emptySet()
        1 -> setOf(single())
        else -> null
    }

    private fun findMaximallySpecific(
        candidates: Set<C>,
        checkArgumentsMode: CheckArgumentTypesMode,
        discriminateGenerics: Boolean
    ): C? =
        if (candidates.size <= 1)
            candidates.firstOrNull()
        else when (checkArgumentsMode) {
            CheckArgumentTypesMode.CHECK_CALLABLE_TYPE ->
                uniquifyCandidatesSet(candidates).singleOrNull {
                    isDefinitelyMostSpecific(it, candidates) { call1, call2 ->
                        isEquallyOrMoreSpecificCallableReference(call1.resultingDescriptor, call2.resultingDescriptor)
                    }
                }

            CheckArgumentTypesMode.CHECK_VALUE_ARGUMENTS ->
                // Attempt 1: general disambiguation
                findMaximallySpecificCall(candidates, discriminateGenerics)

                // Attempt 2: disambiguation excluding SAM converted candidates
                    ?: hasSAMConversion?.let { hasConversion ->
                        findMaximallySpecificCall(
                            candidates.filterNotTo(mutableSetOf(), hasConversion),
                            discriminateGenerics
                        )
                    }

                    // Attempt 3: disambiguation excluding synthetic candidates
                    ?: findMaximallySpecificCall(
                        candidates.filterNotTo(mutableSetOf()) { createFlatSignature(it).isSyntheticMember },
                        discriminateGenerics
                    )

                    // Attempt 4: disambiguation on original SAM-types
                    ?: hasSAMConversion?.let { hasConversion ->
                        findMaximallySpecificCall(
                            candidates.filterTo(mutableSetOf(), hasConversion),
                            discriminateGenerics, useOriginalSamTypes = true
                        )
                    }
        }

    // null means ambiguity between variables
    private fun findMaximallySpecificVariableAsFunctionCalls(candidates: Collection<C>): Set<C>? {
        val variableCalls = candidates.mapTo(newResolvedCallSet(candidates.size)) {
            getVariableCandidates(it) ?: throw AssertionError("Regular call among variable-as-function calls: $it")
        }

        val maxSpecificVariableCalls = chooseMaximallySpecificCandidates(
            variableCalls, CheckArgumentTypesMode.CHECK_VALUE_ARGUMENTS,
            discriminateGenerics = false
        )

        val maxSpecificVariableCall = maxSpecificVariableCalls.singleOrNull() ?: return null
        return candidates.filterTo(newResolvedCallSet(2)) {
            getVariableCandidates(it)!!.resultingDescriptor == maxSpecificVariableCall.resultingDescriptor
        }
    }

    private fun findMaximallySpecificCall(candidates: Set<C>, discriminateGenerics: Boolean, useOriginalSamTypes: Boolean = false): C? {
        val filteredCandidates = uniquifyCandidatesSet(candidates)

        if (filteredCandidates.size <= 1) return filteredCandidates.singleOrNull()

        val conflictingCandidates = filteredCandidates.map { candidateCall ->
            createFlatSignature(candidateCall)
        }

        // This list may be empty, and this is expected.
        val bestCandidatesByParameterTypes = conflictingCandidates.filter { candidate ->
            cancellationChecker.check()
            isMostSpecific(candidate, conflictingCandidates) { call1, call2 ->
                isEquallyOrMoreSpecificCallWithArgumentMapping(call1, call2, discriminateGenerics, useOriginalSamTypes)
            }
        }

        return bestCandidatesByParameterTypes.exactMaxWith { call1, call2 -> isOfEquallyOrMoreSpecificShape(call1, call2) }?.origin
    }

    private inline fun <C : Any> Collection<C>.exactMaxWith(isNotWorse: (C, C) -> Boolean): C? {
        var result: C? = null
        for (candidate in this) {
            if (result == null || isNotWorse(candidate, result)) {
                result = candidate
            }
        }
        if (result == null) return null
        if (any { it != result && isNotWorse(it, result) }) {
            return null
        }
        return result
    }

    private inline fun <C> isMostSpecific(candidate: C, candidates: Collection<C>, isEquallyOrMoreSpecific: (C, C) -> Boolean): Boolean =
        candidates.all { other ->
            candidate === other ||
                    isEquallyOrMoreSpecific(candidate, other)
        }

    private inline fun <C> isDefinitelyMostSpecific(
        candidate: C,
        candidates: Collection<C>,
        isEquallyOrMoreSpecific: (C, C) -> Boolean
    ): Boolean =
        candidates.all { other ->
            candidate === other ||
                    isEquallyOrMoreSpecific(candidate, other) && !isEquallyOrMoreSpecific(other, candidate)
        }

    /**
     * `call1` is not less specific than `call2`
     */
    private fun isEquallyOrMoreSpecificCallWithArgumentMapping(
        call1: FlatSignature<C>,
        call2: FlatSignature<C>,
        discriminateGenerics: Boolean,
        useOriginalSamTypes: Boolean
    ): Boolean {
        return tryCompareDescriptorsFromScripts(call1.candidateDescriptor(), call2.candidateDescriptor()) ?: compareCallsByUsedArguments(
            call1,
            call2,
            discriminateGenerics,
            useOriginalSamTypes
        )
    }

    /**
     * Returns `true` if [call1] is definitely more or equally specific [call2],
     * `false` otherwise.
     */
    private fun compareCallsByUsedArguments(
        call1: FlatSignature<C>,
        call2: FlatSignature<C>,
        discriminateGenerics: Boolean,
        useOriginalSamTypes: Boolean
    ): Boolean {
        if (discriminateGenerics) {
            val isGeneric1 = call1.isGeneric
            val isGeneric2 = call2.isGeneric
            // generic loses to non-generic
            if (isGeneric1 && !isGeneric2) return false
            if (!isGeneric1 && isGeneric2) return true
            // two generics are non-comparable
            if (isGeneric1 && isGeneric2) return false
        }

        if (!call1.isExpect && call2.isExpect) return true
        if (call1.isExpect && !call2.isExpect) return false

        if (call1.contextReceiverCount > call2.contextReceiverCount) return true
        if (call1.contextReceiverCount < call2.contextReceiverCount) return false

        return createEmptyConstraintSystem().isSignatureEquallyOrMoreSpecific(
            call1,
            call2,
            SpecificityComparisonWithNumerics,
            specificityComparator,
            useOriginalSamTypes
        )
    }

    private val SpecificityComparisonWithNumerics = object : SpecificityComparisonCallbacks {
        override fun isNonSubtypeEquallyOrMoreSpecific(specific: KotlinTypeMarker, general: KotlinTypeMarker): Boolean {
            requireOrDescribe(specific is KotlinType, specific)
            requireOrDescribe(general is KotlinType, general)

            val _double = builtIns.doubleType
            val _float = builtIns.floatType

            val isSpecificUnsigned = UnsignedTypes.isUnsignedType(specific)
            val isGeneralUnsigned = UnsignedTypes.isUnsignedType(general)
            return when {
                isSpecificUnsigned && isGeneralUnsigned -> {
                    val uLong = module.findClassAcrossModuleDependencies(StandardNames.FqNames.uLong)?.defaultType ?: return false
                    val uInt = module.findClassAcrossModuleDependencies(StandardNames.FqNames.uInt)?.defaultType ?: return false
                    val uByte = module.findClassAcrossModuleDependencies(StandardNames.FqNames.uByte)?.defaultType ?: return false
                    val uShort = module.findClassAcrossModuleDependencies(StandardNames.FqNames.uShort)?.defaultType ?: return false

                    isNonSubtypeEquallyOrMoreSpecific(specific, general, _double, _float, uLong, uInt, uByte, uShort)
                }

                !isSpecificUnsigned && isGeneralUnsigned -> true

                else -> {
                    val _long = builtIns.longType
                    val _int = builtIns.intType
                    val _byte = builtIns.byteType
                    val _short = builtIns.shortType

                    isNonSubtypeEquallyOrMoreSpecific(specific, general, _double, _float, _long, _int, _byte, _short)
                }
            }

        }

        // It's expected that this function returns `false` for unrelated types like `Int` and `IntArray`.
        private fun isNonSubtypeEquallyOrMoreSpecific(
            specific: KotlinType,
            general: KotlinType,
            _double: KotlinType,
            _float: KotlinType,
            _long: KotlinType,
            _int: KotlinType,
            _byte: KotlinType,
            _short: KotlinType
        ): Boolean {
            when {
                TypeUtils.equalTypes(specific, _double) && TypeUtils.equalTypes(general, _float) -> return true
                TypeUtils.equalTypes(specific, _int) -> {
                    when {
                        TypeUtils.equalTypes(general, _long) -> return true
                        TypeUtils.equalTypes(general, _byte) -> return true
                        TypeUtils.equalTypes(general, _short) -> return true
                    }
                }
                TypeUtils.equalTypes(specific, _short) && TypeUtils.equalTypes(general, _byte) -> return true
            }

            return false
        }
    }

    private fun isOfEquallyOrMoreSpecificShape(
        call1: FlatSignature<C>,
        call2: FlatSignature<C>
    ): Boolean {
        val hasVarargs1 = call1.hasVarargs
        val hasVarargs2 = call2.hasVarargs
        if (hasVarargs1 && !hasVarargs2) return false
        if (!hasVarargs1 && hasVarargs2) return true

        if (call1.numDefaults > call2.numDefaults) {
            return false
        }

        if (platformOverloadsSpecificityComparator.isMoreSpecificShape(call2.candidateDescriptor(), call1.candidateDescriptor())) {
            return false
        }

        return true
    }

    /**
     * Returns `true` if `d1` is definitely not less specific than `d2`,
     * `false` if `d1` is definitely less specific than `d2`,
     * `null` if undecided.
     */
    private fun tryCompareDescriptorsFromScripts(d1: CallableDescriptor, d2: CallableDescriptor): Boolean? {
        val containingDeclaration1 = d1.containingDeclaration
        val containingDeclaration2 = d2.containingDeclaration

        if (containingDeclaration1 is ScriptDescriptor && containingDeclaration2 is ScriptDescriptor) {
            when {
                containingDeclaration1.priority > containingDeclaration2.priority -> return true
                containingDeclaration1.priority < containingDeclaration2.priority -> return false
            }
        }
        return null
    }

    /**
     * Returns `true` if `f` is definitely not less specific than `g`,
     * `false` if `f` is definitely less specific than `g`,
     * `null` if undecided.
     */
    private fun isEquallyOrMoreSpecificCallableReferenceDescriptor(f: CallableDescriptor, g: CallableDescriptor): Boolean {
        if (f.valueParameters.size != g.valueParameters.size) return false
        if (f.varargParameterPosition() != g.varargParameterPosition()) return false

        val fSignature = FlatSignature.createFromCallableDescriptor(f)
        val gSignature = FlatSignature.createFromCallableDescriptor(g)
        if (!createEmptyConstraintSystem().isSignatureEquallyOrMoreSpecific(
                fSignature,
                gSignature,
                SpecificityComparisonWithNumerics,
                specificityComparator
            )
        ) {
            return false
        }

        if (f is CallableMemberDescriptor && g is CallableMemberDescriptor) {
            if (!f.isExpect && g.isExpect) return true
            if (f.isExpect && !g.isExpect) return false
        }

        if (platformOverloadsSpecificityComparator.isMoreSpecificShape(g, f)) {
            return false
        }

        return true
    }

    private fun isEquallyOrMoreSpecificCallableReference(f: CallableDescriptor, g: CallableDescriptor): Boolean =
    // TODO should we "discriminate generic descriptors" for callable references?
        tryCompareDescriptorsFromScripts(f, g) ?: isEquallyOrMoreSpecificCallableReferenceDescriptor(f, g)

    // Different smart casts may lead to the same candidate descriptor wrapped into different ResolvedCallImpl objects
    private fun uniquifyCandidatesSet(candidates: Collection<C>): Set<C> =
        ObjectOpenCustomHashSet(candidates.size, resolvedCallHashingStrategy).apply { addAll(candidates) }

    private fun newResolvedCallSet(expectedSize: Int): MutableSet<C> =
        ObjectOpenCustomHashSet(expectedSize, resolvedCallHashingStrategy)

    private fun FlatSignature<C>.candidateDescriptor() =
        origin.resultingDescriptor.original

    private fun FlatSignature<C>.descriptorVisibility() =
        candidateDescriptor().visibility
}
